The proposed research will contribute to knowledge about racial/ethnic inequalities in health by exploring the nativity paradox - the fact that foreign born mothers, on average, have better birth outcomes than native born mothers of similar socioeconomic status. Using pooled data from three recent studies, we will systematically investigate the extent to which immigrant selectivity contributes to the nativity paradox and we will also test "acculturation" and "weathering" theories by investigating the effects of age at arrival in the U.S. versus duration of residence in the U.S. on birth outcomes. Understanding how the health of immigrants is affected after immigration to the U.S will provide a window into the determinants of racial and ethnic disparities in health in the U.S. PUBLIC HEALTH RELEVANCE: The proposed research will increase knowledge and information about the causes of disparities in birth outcomes among members of minority groups. This new knowledge should lead to more effective interventions for families and subsequently to better birth outcomes and healthier children.